This invention relates generally to shock absorber devices for damping unwanted vehicle motion, such as dipping, bouncing, swaying or leaning, the shock absorber having a reciprocating piston mounted within a cylinder containing a damping fluid, such as oil, where the damping fluid is allowed to flow from one side of the piston to the other in a controlled or restricted manner. More particularly, the invention relates to such devices which are provided with additional stabilizing means to further restrict or block the flow of the damping fluid to maintain the vehicle body in a more stabilized position where the vehicle body is swayed by centrifugal forces during a turn or dips during acceleration or braking. Even more particularly, the invention relates to such devices which further provide means to correct the vehicle body position during turns, acceleration or stops by directing flow of damping fluid in the opposite direction within the cylinder, and where means are provided to limit corrective action at either cylinder end.
Shock absorber devices for damping or reducing unwanted vehicle body motion, usually used in conjunction with large springs, are well known. A shock absorber typically comprises in its most simple form a sealed cylinder having a rod passing through one end, with the rod fastened to the vehicle chassis or body and the other end of the cylinder fastened to the axle, or vice versa. The piston divides the cylinder into an upper and a lower chamber containing a relatively viscous damping fluid. A flow aperture in the piston or a bypass conduit is provided to allow flow of the damping fluid from one side of the piston to the other. Thus when a wheel encounters a bump or a depression in the roadway, the spring member and shock absorber absorb the initial energy, with the shock absorber damping the effects due to the restricted flow of the damping fluid within the cylinder. This limits the tendency of the springs to continue bouncing and limits the amount of movement observed in the vehicle body.
Sudden directional movement or changes caused by turning, accelerating or braking have an undesirable effect on the vehicle body attitude or position due to the effects of inertia and centrifugal force. In a turn, the vehicle body leans in a negative manner due to these forces, with the movement of the vehicle body or chassis causing the piston to move within the cylinder. In a turn to the left, the vehicle right side dips and the vehicle left side rises. In a turn to the right, the opposite occurs. With rapid acceleration the vehicle rear squats and the vehicle nose rises. In stopping, the opposite occurs. The effect of centrifugal force on the turning vehicle is especially detrimental to safe control of the vehicle. Standard shock absorbers are designed to provide a compromise between comfort and road handling ability, such that they are structured in the mid-range between soft to absorb bumps and stiff to limit the unwanted sway, and as such are relatively susceptible to the effects of inertial or centrifugal forces.
Efforts have been made to develop a shock absorber which provides the desired cushioning when the vehicle is driven straight at steady speeds, while simultaneously providing means to stiffen the shock absorber during turns, acceleration or braking to prevent or lessen the centrifugal force effects of the vehicle body. Examples of such devices are seen in U.S. Pat. No. 2,722,288 to Steinbauer, U.S. Pat. No. 2,869,685 to Funkhouser et al., U.S. Pat. No. 2,877,872 to Krizan and U.S. Pat. No. 3,507,366 to King. Each of these patents shows a relatively complicated approach to providing a shock absorber with a valve or set of valves, conduits and chambers, which is reactive to changes in inertia or centrifugal force, which in turn varies the damping characteristics of the shock absorber to stop the undesirable body movement. None of these teachings provides a means to correct the vehicle body position after the movement has been controlled, i.e., a means to return the vehicle body to a more level position and to overcorrect to more optimally align the vehicle body during turning, stopping or accelerating while the vehicle is still subject to the centrifugal or inertial forces. Bock et al. in U.S. Pat. No. 5,383,680 shows an anti-roll system utilizing bypass conduits and one-way valves which provides for only uni-directional piston travel under certain conditions, but which fails to provide limiting means for excessive travel and corrective action, and makes no claim of overcorrecting the vehicle.
It is an object of this invention to provide a self-correcting shock absorber or shock absorber system of relatively simple construction which limits undesirable vehicle body movement resulting from inertial and centrifugal effects during turning, accelerating and stopping, either completely or in a restricted manner, while simultaneously correcting the vehicle body position while the vehicle is still subject to the inertial and centrifugal effects. It is a further object to provide such a system wherein the limitation of undesirable vehicle body movement is controlled by providing a means to sense the change in centrifugal force which in turn blocks or restricts normally open flow apertures within the shock absorber cylinder to prevent flow of damping fluid in the reactive direction. It is a further object to provide such a system wherein the correction of vehicle body position is accomplished by providing one way check or pressure relief type valves, whereby relatively small variations in the road surface cause damping fluid to flow in the opposite or non-reactive direction to move the piston, and thereby the vehicle body, in the desired direction to level out the body position and to overcorrect body position for optimum alignment during turning, stopping or accelerating. It is a further object to provide piston travel limiting means, such that the corrective action is precluded when the piston travels to either end of the cylinder and which allows the shock absorber to function in the normal mode to damp road shocks.
The invention comprises in general a shock absorber having a sealed cylinder containing a damping fluid or oil, a rod extending through one end of the cylinder, to which is attached a piston which divides the cylinder interior into an upper chamber and a lower chamber, and conduit means to allow the damping fluid to pass between the upper chamber and the lower chamber, where the piston and rod are free to reciprocate within the cylinder. The shock absorber is mounted in conventional manner to a motor vehicle between the chassis or body and the axle so as to dampen sudden movements of the vehicle wheel caused by bumps or depressions in the roadway.
The invention further comprises means to sense changes in vehicle inertia, such as turning, accelerating or stopping, which may comprise means to sense changes in centrifugal force or means to directly monitor steering, braking or accelerating components of the vehicle. The inertia sensing means operatively communicates with means to block or restrict flow of damping fluid in the reactive direction from the high pressure or contracting chamber in the cylinder to the low pressure or expanding chamber, whereby the flow is stopped or severely restricted in response to a change in inertia. The invention further comprises means to deliver damping fluid in the corrective direction opposite to the reactive direction, i.e., from the expanding chamber to the contracting chamber.
When a change in inertia or centrifugal force is sensed, the fluid flow restricting means blocks the flow of damping fluid through the conduit means, typically a flow orifice in the piston, which prevents the piston from moving relative to the cylinder, thus preventing movement of the vehicle body in the direction resulting from centrifugal effects. The shock absorber is thus transformed into a fixed rod, if flow is completely blocked, or a very stiff shock absorber, if some flow is allowed to continue in the reactive direction from the contracting chamber to the expanding chamber. At the same time, relatively small variations in the road surface apply pressure to the shock absorber in the direction opposite to the pressure from the centrifugal forces, which causes damping fluid to flow through the one way valves in the corrective direction, thus in effect pumping fluid from the expanding chamber into the contracting chamber. This forced fluid flow causes the piston to move in the direction opposite to the direction of imposed force from the centrifugal effects, thereby leveling the vehicle body and, if the centrifugal effects continue long enough, actually over-correcting the vehicle body to cause it to lean or bank into a turn, to lower the nose and raise the rear during acceleration, or to raise the nose and lower the rear during braking.
The invention further comprises piston travel limiting means to limit travel of the piston in either corrective direction to prevent the piston from contacting the ends of the cylinder due to the corrective movement and to allow the piston to move in either direction in response to road conditions. The travel limiting means comprise at least a pair of flow paths for the damping fluid, one adjacent each end of the cylinder, which extend in the axial direction a distance greater than the height of the piston and open into the interior of the cylinder. Each flow path has two openings which communicate with the interior of the cylinder. When the piston is positioned between the two openings of a flow path, damping fluid will bypass the piston so that corrective action is canceled, returning the shock absorber to a normal operational mode whereby the piston will respond to bumps and depressions with motion in the appropriate direction.